Chlorophyll a, total phosphorus, total organic carbon, true colour, total iron, total manganese, water temperature and turbidity did not meet the guidelines for drinking water at times. Total phosphorus and extinction depth did not meet the guidelines for primary and secondary recreation at times, and total phosphorus and dissolved oxygen did not meet the guidelines to protect aquatic life at times.
Given the above, we recommend that a remediation plan be developed and implemented to improve water quality in Cusheon Lake. The plan should be developed and implemented by a Cusheon Lake watershed group in conjunction with Islands Trust. The focus of the remediation plan would be:
· to determine the suitability of Cusheon Lake for recreation, drinking water and sustaining aquatic life;
· to identify the sources of nutrients and contaminants in the watershed and lake;
· to identify what is required to improve the water quality in Cusheon Lake to make it suitable for recreation, drinking and sustaining aquatic life; and
· to evaluate remediation options and recommend the most efficient approach to improving water quality in the lake.
We recommend monitoring be continued at the deep station on Cusheon Lake (EMS site 1100123). Water quality samples should be collected during spring overturn and monthly between June and October. The results from these samples will be used to determine the water quality in Cusheon Lake and to set water quality objectives to protect water uses. Also, these results may be used to recommend and evaluate possible remediation activities. This monitoring program, at the deep station on Cusheon Lake, would require sampling of the following water quality indicators:
_ water temperature and dissolved oxygen collected at
one-metre intervals from the surface to the bottom;
_ duplicate chlorophyll a samples collected at zero, two,
four, six metre water depths. These samples should be collected every four weeks between May to August;
_ total phosphorus, dissolved ammonia, nitrate/nitrite, Kjeldahl nitrogen, total and dissolved organic carbon,
true colour, turbidity, pH, dissolved silica from three samples taken one metre below the surface, at mid-depth and one metre above the bottom;
_ total metals; and
_ extinction depth (i.e., Secchi depth) and UVb absorption.
The Cusheon Lake watershed should be inspected and monitoring conducted to identify and quantify the sources of nutrients and contaminants entering the lake. This monitoring should be done year-round for one year, at a frequency ranging from weekly during wet, high flow conditions to monthly during dry conditions, and include flow, total phosphorus, dissolved ammonia, nitrate/nitrite, Kjeldahl nitrogen, total and dissolved organic carbon, true colour, turbidity, total metals, and fecal coliforms.
A Cusheon Lake stewardship group could implement this monitoring program with assistance from the Ministry of Environment, Lands and Parks.
We recommend that bacteriological sampling continue at the public access on Cusheon Lake. The Capital Health Region is currently conducting the monitoring program. In future, a Cusheon Lake stewardship group could assist with this ongoing monitoring.
We recommend that the water works licensee (Beddis Water Works District) monitor the chlorinated water for trihalomethanes. The results of this monitoring should be reported, on a quarterly basis, to the Capital Health Region.
We recommend that bacteriological and water quality sampling be conducted at the 35 domestic water licenses on Cusheon Lake that may be used as a drinking water sources. Ten fecal coliform samples, taken in any consecutive 30-day period, within 10 m of domestic intakes should be collected to determine the suitability of the water for drinking and the level of treatment needed. Also, water quality samples should be collected with the fecal coliform samples and should be analyzed for total phosphorus, organic carbon, true colour, total iron, total manganese, water temperature, and turbidity. A Cusheon Lake stewardship group could implement this monitoring program with assistance from Capital Health Region and/or the Ministry of Environment, Lands and Parks.